The U.S. will implement a travel ban on North Korea stating Sept. 1, the State Department announced Wednesday, months after the death of an American college student who returned from the rogue nation in a mysterious coma.

The State Department cited the “serious and mounting risk of arrest and long-term detention of U.S. citizens” as its justification for the ban, which will last at least one year.

Officials said anyone holding a U.S. passport in North Korea now should leave the isolated country before the ban goes into place. Only certain groups of people, including journalists and humanitarian workers, can apply for exceptions to the ban.

A North Korean missile test in July.

Despite President Trump’s push for bans on travelers from certain countries, this is the first time his administration has prohibited U.S. citizens from traveling somewhere else.

The U.S. said it would likely begin a ban after the death of Otto Warmbier, a University of Virginia student who was detained in Pyongyang’s airport as he prepared to leave the country Jan. 2, 2016.

In a sham trial, North Korea convicted Warmbier of a “hostile act” against the state for allegedly stealing a propaganda banner from a hotel. He was sentenced to 15 years of hard labor, and was never heard from again until North Korea sent him back to the U.S. in June in a coma. He died six days later.

University of Virginia student Otto Warmbier died in June after returning from North Korea in a coma.

(KYODO Kyodo/REUTERS)

North Korea claimed Warmbier lost consciousness due to botulism and a sleeping pill, but U.S. doctors doubted those claims and said the 22-year-old student suffered “severe injuries to all areas” of his brain. It remains unclear what happened to him during his captivity.

At least 16 U.S. citizens have been detained in North Korea in the past 10 years, and at least three are being held there now.

The ban came as tensions between the U.S. and North Korea skyrocket while Kim Jong Un’s empire accelerates its capabilities for long-range missiles. Trump on Wednesday signed a bill that slaps sanctions on North Korea, as well as Iran and Russia, for human rights violations.